Welcome to Rafael's web page.
I have been a visitor at Caltech's Theoretical Astrophysics group (a.k.a.
TAPIR)
since year 2000 first working on various Magnetohydrodynamic and General Relativity problems in Astrophysics
and more recently on formulations of Quantum Gravity which incorporate a small, non-vanishing cosmological constant.

Nascent black holes are conjectured to occur at the cores of very massive stars to yield
Gamma-ray Bursts. As
I set out to understand the magnetic nature of accretion flows onto black holes, I was the first theorist to carry out a
fully general relativistic analysis
of the problem (in the Cowling approximation). In a subsequent paper, I make the
prediction
that the black hole may be driven into a strongly vibrating mode by heavy clumps of material falling in through the "event horizon" in unison
with the hole's natural oscillating tempo. The energy of such vibrations would radiate away in a very uniform pattern of
Gravitational Waves that may someday be observed by
LIGO.
Here is a
link with the latest on GRB observations.

After a rendezvous with
mathematical finance and game theory, I've been drawn back to the realm of theoretical physics by the cosmological constant problem.
Standard fare in modern physics posits that empty space is endowed with quantum energy.
Although quantum physics and general relativity are fundamentally inconsistent with each other, the mathematical framework invoked by Albert
Einstein to construct the General Theory of Relativity admits an extra
term--a.k.a. the cosmological term--that accounts for the "virtual" energy of the vacuum.
Taken at face value, such conjecture leads to an outlandish dynamical effect: a "speeding up" in the expansion of the fabric of space-time
associated with the growth of vacuum in the Universe.
Astonishingly, today we know that the expansion of the Universe has indeed been accelerating for well over half of the time the Universe's
been around! Yet, this effect is much too weak to fit into the standard model of our interpretation of "the" physical vacuum!
I am chiefly concerned with fundamentally geometrical constructions of [Quantum] Gravity where a non-vanishing cosmological constant
arises naturally as a by product of interpreting Gravity as the gauge theory of an underlying symmetry principle,
i.e., gauging the De Sitter group in a quasi--Yang-Mills form.
Here is a collection of
interesting papers.